1. Field of the Invention
The invention relates to a semiconductor component with a passivation layer and a method for its production. Passivation is understood to mean the coating of flat or structured components such that the electrical properties of the component are not a function of the ambient atmosphere.
2. Discussion of Background Information
The surface of a semiconductor represents a disturbance of the periodic lattice that changes the electrical properties of the semiconductor considerably. This causes the formation of surface states that can be modified by the chemisorption or physisorption of adsorbates. The result is a space-charge zone, the expansion and character of which largely determine the properties of the surface. This exerts an impact onto the position of the Fermi level in the active region of the component and consequently to a dependence of the electrical properties on the ambient atmosphere, e.g., air humidity and/or process chemistry. The consequence of the changing surface states are surface leakage currents that raise the noise level of a semiconductor component. The performance of active components, in particular those made of materials with a small bandgap (e.g., infrared photodiodes), is essentially dependent on the noise contributions. Therefore, an effective passivation is essential in particular for the permanent suppression of surface leakage currents and for the stabilization of the electrical properties of the surface of the component.
Generally, components based on elemental semiconductors such as silicon or germanium and the III-V-semiconductors are passivated by applying a layer of insulator material. Customary materials for this are SiO2, SixNy, or SiOxNy. These are applied by various deposition methods, e.g., low pressure chemical vapor deposition (LPCVD), plasma enhanced chemical vapor deposition (PECVD), or sputtering.
Semiconductor components with a small bandgap, e.g., mercury-cadmium-telluride (MCT) can be conventionally passivated by a material with a larger bandgap, e.g., CdTe. The effect of the passivation rests hereby on the combination of the semiconductor CdTe having a large bandgap (Eg=1.6 eV) with the diode material of the component having a smaller bandgap (Eg<350 meV). As a result, an expansion of the effective bandgap occurs in the region of the diode. This leads to a depletion of the respective minority charge carrier in the border area of the diode and thus to a reduction in the surface leakage currents. The methods and processes for the production as well as the processing of MCT are elaborate, error-prone, and cost-intensive.
Furthermore, semiconductor components with a small bandgap can also be produced on the basis of the alloy AlxGayIn1-x-yAszSb1-z. Depending on the parameters x, y, and z, a bandgap of less than 350 meV can be achieved.
Components with small bandgaps can be produced in particular by application of heterostructures and superlattices of two different alloys, such as, e.g., InAs and Ga1-xInxSb single layers with thicknesses of between 2 nm and 10 nm. However, the passivation of such components has not hitherto been possible in a simple manner.